Method of Defrosting a Heat Pump Device as Well as a Heat Pump Device

ABSTRACT

A method of defrosting a heat pump device including a water tank, a heat exchanger, an electrical heating element, an evaporator, a fan for the evaporator, and a control unit. In a first operating mode, the heat pump device is controlled to heat water inside the water tank. In a second operating mode, the electrical heating element is manually activated to additionally heat the water inside the water tank. In a third operating mode, the electrical heating element is automatically activating to heat the water in the storage tank if: a) the power supplied by the heat pump device to heat the water inside the water tank is not sufficient; b) if a time limit after activation of a deicing operation has lapsed; and/or c) if the number of times the deicing operation has been activated during a predetermined time interval exceeds a threshold value.

FIELD OF THE INVENTION

The present invention relates to a method of deicing or defrosting aheat pump device as well as a heat pump device.

It is noted that citation or identification of any document in thisapplication is not an admission that such document is available as priorart to the present invention.

If a heat pump device is operated at low temperature conditions, watercan condense on the evaporator of the heat pump device. If the outsidetemperature is high enough, the freezing agent is above the freezingtemperature. If the outside temperature, however, drops, then therefrigerant circuit can be operating at a temperature below the freezingtemperature and the water which has condensated on the evaporator isstarting to freeze such that a hoar frost build-up is starting at theevaporator.

In particular, the water which is present between the fins of theevaporator starts to freeze such that the distance between adjacentfins, through which typically air is streaming, is reduced and theamount of air which can stream there through is reduced. In the worstcase, the air stream is blocked such that no air can stream through theevaporator. In such a situation, a deicing or defrosting is required.

For deicing or defrosting the evaporator, the compressor can be switchedon and off in a cyclic manner. During the deicing or defrosting, thecompressor is stopped such that the freezing agent is not flowing anymore through the refrigerant circuit. On the other hand, the fan of theevaporator is still operating such that air is streaming through theevaporator and the ice between the fins is deiced or defrosted by theenergy which is still present in the outside air. This deicing operationis only possible if the air temperature is above the freezingtemperature. On the other hand, if the air is below 2° C. (35.6° F.),the defrosting operation can have a negative impact on the comfort ofthe user of the heat pump device as the ability of the heat pump deviceto produce sufficient hot water is reduced, i.e. the time required toheat sufficient water is increasing.

It should further be noted that the rate at which ice or hoar frostbuild-up is present at the fins of the evaporator is not only dependenton the temperature of the outside air, but also the humidity of the air.In other words, the heat pump device must react differently to lowtemperatures which have a low air humidity than compared to lowtemperatures which also have a high air humidity. In the first case, theheat pump device may initiate a defrosting of the evaporator while adefrosting is not yet required.

It is noted that in this disclosure and particularly in the claimsand/or paragraphs, terms such as “comprises”, “comprised”, “comprising”and the like can have the meaning attributed to it in U.S. Patent law;e.g., they can mean “includes”, “included”, “including”, and the like;and that terms such as “consisting essentially of” and “consistsessentially of” have the meaning ascribed to them in U.S. Patent law,e.g., they allow for elements not explicitly recited, but excludeelements that are found in the prior art or that affect a basic or novelcharacteristic of the invention.

It is further noted that the invention does not intend to encompasswithin the scope of the invention any previously disclosed product,process of making the product or method of using the product, whichmeets the written description and enablement requirements of the USPTO(35 U.S.C. 112), such that applicant(s) reserve the right to disclaim,and hereby disclose a disclaimer of, any previously described product,method of making the product, or process of using the product.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method of defrosting ordeicing a heat pump device which enables an effective deicing ordefrosting.

This object is achieved by a method of deicing or defrosting a heat pumpdevice as well as a heat pump device, as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of a heat pump device accordingto an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the present invention, while eliminating,for purposes of clarity, many other elements which are conventional inthis art. Those of ordinary skill in the art will recognize that otherelements are desirable for implementing the present invention. However,because such elements are well known in the art, and because they do notfacilitate a better understanding of the present invention, a discussionof such elements is not provided herein.

The present invention will now be described in detail on the basis ofexemplary embodiments.

FIG. 1 shows a schematic representation of a heat pump device accordingto an embodiment of the invention. The heat pump device HP isimplemented as an air/water heat pump device 1, HP. The heat pump device1 comprises a storage tank 7 adapted for tap water or drinking water, aplate heat exchanger, in particular a roll bond (plate) heat exchanger 8which can be arranged around the storage tanks 7. Inside the storagetank 7, an electrical heating element 5, HE can be arranged. The heatpump device 1 furthermore comprises an evaporator 3 with a fan 4. Acompressor, an expansion valve and a filter dryer are not disclosed inFIG. 1.

Furthermore, the heat pump device 1 comprises a first temperature sensorT1 which is measuring the temperature of the air in or at the evaporatorwhich is sucked in by the fan 4 as well as a second temperature sensorT2 which is arranged adjacent to or at the evaporator 3. The secondtemperature sensor T2 is used to detect a hoar frost or ice build-up atthe evaporator 3.

The heat pump device 1 furthermore comprises a control unit 9 which isadapted to control the operation of the electrical heating element 5 inorder to control the temperature of the water inside the storage tank 7.Optionally, the heat pump device 1 may comprise a user interface or anoperating element 10. By means of the user interface or the operatingelement 10, the user can choose the set value of the temperature of thewater inside the storage tank. Moreover, the user interface or theoperating unit 10 can be used by the user to initiate an additionalheating of the water inside the storage tank by means of the heatingelement 5.

The electrical heating element 5 can be implemented as a tubular heatingelement or as a heating rod. The roll bond heat exchanger 8 (as part ofthe heat pump) is used as primary heating source for heating the waterinside the storage tank 7. The heating element 5 is used as secondaryheating element e.g. for situations where the roll bond heat exchanger 8is not able to provide sufficient energy to sufficiently heat the waterinside the storage tank 7.

It should be noted that the primary heating via the roll bond heatexchanger 8 is more energy sufficient than the heating via the secondaryelectrical heating element, namely the heating element 5.

The heat pump device can be operated in different operating modes. Thedifferent operating modes can for example be activated by the controlunit 9 in particular depending on the temperature as detected by thesecond temperature sensor T2 as well as the first temperature sensor T1.

The second temperature sensor T2 is used to detect the hoar frostbuild-up at the evaporator. The temperature as sensed by the secondtemperature sensor T2 is compared in the control unit 9 with a storedset value. If the temperature as detected by the second temperaturesensor T2 is below the set value, the heating operation of the heat pumpdevice is stopped and the defrosting operation is initiated. Thedefrosting operation is continued until the hoar frost build-up at theevaporator is removed. This is in particular performed by melting theice on the evaporator.

As mentioned above, the defrosting or deicing can be performed bydeactivating the compressor while the fan 4 of the evaporator 3 is stillin operation until the temperature as detected by the second temperaturesensor T2 is above 0° C. For example, if the temperature as detected bythe second temperature sensor T2 is for example 3° C., then thecompressor can be activated again and thus the heating operation of theheat pump device can be activated again. The time required fordefrosting or deicing the evaporator will depend on the amount of ice orhoar frost build-up on the evaporator.

The normal operating mode can be considered as the first operating mode.During this operating mode (heating operating mode), the heat pumpdevice is heating the water inside the storage tank 7 via the roll bondheat exchanger 8 and the heating element 5 is deactivated.

In a second operating mode, the user may manually activate the operationof the heating element 5 for example via the user interface or operatingunit 10. Via the heating element 5, a part of the water inside thestorage tank is heated one time. If the water temperature inside thestorage tank 7 corresponds to the desired value, then the heatingelement 5 is deactivated again and only the heat pump device is heatingthe water inside the storage tank 7 via the roll bond heat exchanger 8.

The control unit 9 activates a third operating mode if the temperatureas detected by the first temperature sensor T1 is below a set valuewhich can be for example 6° C. In the third operating mode, theoperation of the heating element 5 is controlled by the control unit 9.The control unit 9 controls the operation of the heating element 5 inparticular if a second condition is fulfilled. The heating element 5 isonly then activated automatically by the control unit 9 if the heat pumpdevice 1 is not able to produce sufficient hot water via the roll bondheat exchanger 8. In addition or alternatively, the heating element 5 isactivated via the control unit 9 if the time during which the deicingoperation is activated exceeds a time limit, for example like 30minutes. If this time limit has lapsed, then the control unit 9activates the operation of the heating element 5 and the operation iscontinued until the heating requirement is fulfilled. Accordingly, theheating requirement may relate to a normal operation of the heat pumpdevice with an increased requirement for hot water or alternatively ifthe deicing operation is continued beyond a set time period.

In addition or alternatively, the control unit 10 can also activate theoperation of the heating element 5 if the defrosting operation isactivated several times within a set time period. For example, if thedefrosting operation is activated five times during two hours, thecontrol unit 10 activates the operation of the heating element 5 to heatthe water inside the storage tank. This activation of the heatingelement can continue until the number of activations of the defrostingunit within a set time limit has decreased.

If the control unit 9 deactivates the heating operation of the heat pumpdevice via the roll bond heat exchanger 8, the automatic operation ofthe heating element 5 via the control unit 9 is also deactivated.

If the air temperate as determined by the second temperature sensor T2has increased for example up to 8° C., the third operating mode(automatic operation of the heat element) is deactivated such that theheating element can only be manually activated via the user interface oroperating unit 10.

Therefore, the on and off switching of the manual and automaticoperation of the heating element includes a hysteresis of for example 2°C.

The control unit 9 activates a fourth operating mode if the airtemperature as determined by the second temperature sensor T2 is below2° C. and the necessity of a defrosting operation is detected. If thedefrosting operation is continuing for more than 30 minutes, the fan 4of the evaporator 3 is deactivated and the control unit 9 activates theoperation of the heating element 5 until a temperature control device(thermostat) of the heat pump device together with the control unit 9deactivates the operation of the heating element 5. During thisoperating mode, the operation of the heat pump device is deactivated fora predetermined time interval. The deactivation of the heat pump deviceoperation starts with the deactivation of the fan 4. The time period ofthis deactivation can be for example up to 4 hours. If the temperatureof the air flowing through the evaporator 3 as determined by the firsttemperature sensor T1 is above 6° C., the time period for thedeactivation of the heat pump device 1 is reduced. If the airtemperature as determined by the second temperature sensor T2 is above8° C. or if a power outage occurs, the heating operation of the heatpump device is activated again.

If the temperature of the air as determined by the first temperaturesensor T1 is below −2° C., the heating operation of the heat pump deviceis deactivated and the automatic operation of the heating element 5 isactivated. This operation is deactivated again when the temperature asdetermined by the first temperature sensor T1 is >0° C.

According to an aspect of the invention, the fan 4 is activated for 5 to10 seconds before the temperature sensor T1 determines the temperatureof the air flowing through the evaporator. This is advantageous as thiswill allow a more accurate measuring of the air temperature. Thetemperature as measured by the temperature sensor T1 is used to decidedwhether or not the compressor can be activated again and the heatingoperation of the heat pump device can be reactivated again.

In an aspect of the invention, the fan 4 can be activated before thetemperature sensor T1 detects the air temperature of the air flowingthrough the evaporator in case the heat pump device has beendeactivated.

In a further aspect of the invention, the last temperature value whichwas measured by the temperature sensor T1 during an active operation ofthe fan can be used when the heating operation of the heat pump has beendeactivated in order to determine whether or not the compressor is to beactivated again.

In the following table, different operating modes of the heat pumpdevice HP and the electrical heating element HE are depicted:

HP Air HP de- HE HE HP blocked = HP temperature heating frosting manualauto f (defrosting) blocked >6° C. X X X <6° C., >2° C. X X X X <3°C. >0° C. X X X X X <−2° C. X X X

While this invention has been described in conjunction with the specificembodiments outlined above, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, the preferred embodiments of the invention as setforth above are intended to be illustrative, not limiting. Variouschanges may be made without departing from the spirit and scope of theinventions as defined in the following claims.

1. A method of defrosting a heat pump device which comprises a watertank, a heat exchanger coupled to the water tank, an electrical heatingelement inside the water tank, an evaporator, a fan for the evaporatorand a control unit adapted to control an operation of the heat pumpdevice and the electrical heating element, comprising the steps of: in afirst operating mode, controlling the heat pump device to heat waterinside the water tank; in a second operating mode, manually activatingthe electrical heating element to additionally heat the water inside thewater tank; and in a third operating mode, automatically activating theelectrical heating element to heat the water in the storage tank if: a)the power supplied by the heat pump device to heat the water inside thewater tank is not sufficient; b) if a time limit after activation of adeicing operation has lapsed; and/or c) if the number of times thedeicing operation has been activated during a predetermined timeinterval exceeds a threshold value.
 2. The method according to claim 1,further comprising the steps of: in a fourth operating mode, if the airtemperature is below 2° C. and if a defrosting requirement has beendetected, deactivating the fan of the evaporator and activating theoperation of the electrical heating element; and deactivating theoperation of the heat pump device for a predetermined time interval. 3.The method according to claim 2; wherein a time period of deactivatingthe heat pump device is reduced if the temperature of the air flowingthrough the evaporator is above 6° C.
 4. A heat pump device comprising:a water tank; a heat exchanger coupled to the water tank; an electricalheating element inside the water tank; an evaporator; a fan for theevaporator; and a control unit adapted to control an operation of theheat pump device and the electrical heating element; wherein saidcontrol unit configured to: in a first operating mode, control the heatpump device to heat water inside the water tank; in a second operatingmode, manually activate the electrical heating element to additionallyheat the water inside the water tank; and in a third operating mode,automatically activate the electrical heating element to heat the waterin the storage tank if: a) the power supplied by the heat pump device toheat the water inside the water tank is not sufficient; b) if a timelimit after activation of a deicing operation has lapsed; and/or c) ifthe number of times the deicing operation has been activated during apredetermined time interval exceeds a threshold value.